The present invention relates to an ink jet head and a method of producing the same and, more particularly, to a head for an on-demand ink jet printer and a method of producing the same.
Today, an on-demand ink jet printer is extensively used because it features high image quality for its cost. However, the problem with an on-demand ink jet printer is that it is lower in printing speed than, e.g., a laser printer. Some different approaches have been proposed to implement high density for enhancing high speed printing with an on-demand ink jet printer. Japanese Patent Laid-Open Publication No. 6-23986, for example, uses a single crystal Si (100) substrate for a first Si substrate and subjects it to anisotropic etching while matching the short side or width of a vibration plate to the dimension of a mask opening. Specifically, after the first Si substrate has been formed with gaps which will turn out liquid chambers, the substrate is bonded to a second Si substrate. Then, the second substrate is etched and ground in order to form vibration plates. Subsequently, the laminate is bonded to a glass substrate formed with gaps and counter electrode by anodic bonding. when the Si substrate having a thickness of 3 xcexcm and the glass substrate formed with the gaps having a depth of about 1 xcexcm are bonded by anodic bonding, a voltage of several hundred volts is applied to the gaps and causes the vibration plate to deform.
Because the above deformation of the vibration remains, it is necessary to short-circuit the vibration plates and associates counter electrodes during anodic bonding.
However, it is extremely troublesome to short-circuit all of more than 100 vibration plates included in a single chip;
moreover, a single wafer includes about 100 chips. In addition, chips located at the central portion of a wafer cannot be easily short-circuited. Further, because electrochemical etching follows the bonding of the first and second Si substrates, the substrate with the gaps for implementing ink chambers must be protected by special processing during etching. For example, it is necessary to form a thick thermal oxide film in order to etch out only a portion corresponding to the bonding surface, or to apply a thick organic resist for obstructing etching.
It is therefore an object of the present invention to provide an ink jet head using a sufficiently thick single crystal at the time of anodic bonding and thereby obviating the deformation of a vibration plate without resorting to any special short-circuit electrode, and a method of producing the same.
An ink jet head of the present invention includes a substrate, a plurality of nozzles, a plurality of ink passageways each being communicated to the respective nozzle, a vibration plate positioned in a part of each of the ink passageways, a plurality of independent electrodes formed on the substrate and facing the vibration plate, and a common electrode formed on the vibration plate. A drive voltage is applied between the common electrode and any one of the independent electrodes for causing the vibration plate to electrostatically deform, thereby ejecting a drop of ink from one of the nozzles associated with the above independent electrode. The vibration plate is implemented by single crystal Si while the substrate is implemented by glass having a coefficient of linear expansion close to that of the single crystal Si at temperatures between 200xc2x0 C. and 400xc2x0 C. After the single crystal Si has been bonded to the substrate by anodic bonding, the single crystal Si is thinned to a preselected thickness by etching or grinding, and then an ink passageway, ink chamber and nozzle section is adhered or bonded to the substrate.